In a factory where aluminum is molded using many die-casting machines, an aluminum material is often supplied not only from within the factory but also from outside of the factory. In such a case, a container storing aluminum in a melt is carried from a factory on the material supply side to a factory on the molding side to supply to each of a storing furnace of the die-casting machines the material kept in the melt. As an embodiment, a system of applying pressure to an inside of the container and supplying a molten metal from the container to the storing furnace using a pressure difference is recommended (for example, Japanese laid-open utility model application publication H03-31063 (first drawing)).
The technology according to the publication mentioned above is structured such that the supply of molten aluminum from the container to the storing furnace side starts as pressure is being increased and when the supply is stopped later, the supply of the gas from the outside to the inside is switched to exhaust inside of the container, in order to have pressure in the container to become at a state of the atmospheric pressure (page 10 line 7 to line 11 of Japanese laid-open utility model application publication H03-31063).
As the container of this kind stores a molten metal of extremely high temperature, the possibility of having to shutdown the process of applying pressure to the container for some reasons in an emergency is very high. According to the publication, it is possible to cope with such emergency shutdown by switching from supplying gas to exhausting gas.
Nevertheless, in an unexpected event where the switching did not function properly due to electronic trouble and the like caused by noise in the factory, or exhaustion was not performed, there is a very high risk of inducing a serious accident. For this reason, providing, for example, a manually operated valve open to the atmosphere and a valve for blocking the flow passage and manually operate these valves in the event of an emergency may be considered. However, there is a problem that, in such case, switching operation of the two valves is required.
Furthermore, according to the above publication, pressure is applied to inside of the container by a gas supply device mounted on a forklift.
Nevertheless, there is a problem that with such gas supply device, inside of the container cannot be applied with steady pressure.
In such case, for example, compressed gas supplied from pipes running inside the factory may be used. However in that case the container placed on a vehicle such as forklift has to be connected to the factory side through a pipe, which has a negative effect on operability.